Pope John Paul II is expected to spend a week in hospital, where he is recovering from an acute respiratory infection, a Vatican spokesman said.
The world's Catholics are praying for the Pope's recovery
His condition is said to be improving after passing a "calm" night at Rome's Gemelli hospital.
The pontiff, who has been in frail health for several years, was taken to hospital on Tuesday after being struck by influenza at the weekend.
The infection is now said to be in regression, the Vatican says.
In a medical bulletin issued by papal spokesman Joaquin Navarro-Valls, the Vatican says the Pope has not suffered any further throat spasms.
"The Holy Father's general and respiratory conditions show a positive evolution," Mr Navarro-Valls said.
The 84-year-old Pope apparently suffered a laryngo-spasm, a closure of the larynx that blocks the passage of air to the lungs.
But the BBC's David Willey in Rome says breathing difficulties persist and there remains a risk of complications.
Vatican Secretary of State Cardinal Angelo Sodano, the mini-state's second highest official, said the Pope's condition could have been treated at home.
"But the Holy Father, like everyone else, follows the advice of his doctors," he said.
Another Vatican spokesman, Javier Lozano Barragan, said he would remain in the hospital "to stay ready for any complications".
There are concerns that he could develop pneumonia, although his heart and lungs are currently said to be normal.
Our correspondent says the Vatican is at pains to stress that this is not a life-threatening illness.
Reports say the Pope may make an address from the hospital this weekend.
Catholics around the world have attended special church services to pray for his recovery.
Cardinal Sodano thanked them for their prayers, saying they were a "great sign of comfort" and demonstrated people's affection for the Pope.
The Pope suffers from Parkinson's disease and painful joint conditions.
The Pope's latest health scare has caused concern around the world
He was forced to cancel all engagements for several days after coming down with flu on Sunday.
Vatican sources say a contingency plan was made for the Pope to be taken to hospital if he fell victim to the current flu epidemic sweeping Italy. A set of rooms is always reserved for him on the 10th floor.
The appointment of Karol Wojtyla as the first Polish pope in 1978 was seen as a groundbreaking move for the Roman Catholic Church.
The first non-Italian pope in 455 years - and at 58, the youngest pope of the 20th Century - he was little known outside Vatican circles. Few experts tipped him as successor to Pope John Paul, who died after only 33 days in office.
John Paul II is now in the 27th year of his pontificate which makes him almost the longest-reigning pope in history.
The Pope - the leader of the world's estimated one billion Catholics - has visited more than 100 countries, and is estimated to have effectively circled the globe 27 times.